[GRASS-user] new addon for multivariate surface interpolation from sparse points with smoothing

[Markus Metz]

On Fri, Aug 26, 2016 at 5:28 AM, Vaclav Petras <wenzeslaus at gmail.com> wrote:
> Hi Markus,
>
> On Thu, Aug 25, 2016 at 3:02 PM, Markus Metz <markus.metz.giswork at gmail.com>
> wrote:
>>
>> The new addon v.surf.tps performs multivariate thin plate spline
>> interpolation of sparse points with smoothing.
>
> really interesting. I did some preliminary tests and I might provide some
> feedback later. For now I updated the examples in the manual in r69259, so
> please update your svn copy.
>
>> If you ever wondered
>> why worldclim data (http://worldclim.org) follow so nicely elevation,
>> the reason is multivariate thin plate spline interpolation of
>> meteorological station data with elevation as a covariate.
>> [...] The module works only with GRASS 7.2+.
>
> It may be useful to note that you can preform similar operation with any
> version of GRASS GIS using v.vol.rst (3D interpolation using regularized
> spline with tension). The trick is using cross_* parameters to extract the
> desired 2D raster.

For one covariable, yes, but not for more covariables. E.g. worldclim
has been interpolated using elevation, latitude and longitude as
covariables. And v.vol.rst is rather slow.

Markus M

> Here is an example from [2]:
>
> g.region raster=elev_state_500m -p
> g.region t=2000 b=0 tbres=2000 res3=500 -p3
> v.vol.rst input=precip_30ynormals_3d \
>     cross_input=elev_state_500m cross_output=precip_anntopo_500m \
>     maskmap=elev_state_500m wcolumn=annual zscale=90 segmax=700
>
> Thanks!
> Vaclav
>
> [1] https://trac.osgeo.org/grass/changeset/69259
> [2]
> http://ncsu-geoforall-lab.github.io/geospatial-modeling-course/grass/interpolation_2.html